Separate cauliflower and cut into small pieces. Boil with chicken & bacon stock until very tender. Fry bacon until crisp, place on paper towel to drain. Saute onion in bacon fat until soft, about 8 minutes.
Place onion and cooked cauliflower in food processor with some of the broth (how much broth depends on how thick you want it). Add butter and cream and pulse until creamy. Sprinkle in salt and pepper to taste.